Known road finishers include a hopper at the front of the road finisher with respect to the paving direction to accommodate paving material. During paving, the paving material is conveyed from the hopper to the rear of the road finisher via a suitable longitudinal conveyor. There, a spreading auger distributes the paving material transverse to the paving direction, thus feeding it evenly to a paving screed pulled behind by the road finisher for compacting the paving material. It is known from practice to attach the spreading auger to the road finisher chassis in a height-adjustable manner. By adjusting the height of the spreading auger relative to the chassis, the road finisher can be adapted for paving different layer thicknesses. For example, the spreading auger can be lifted relative to the chassis to pave thicker layers.
A disadvantage of such a system is that for paving very thick layers the position of the auger relative to the chassis is significantly changed upwards. This can lead to a situation where the spreading auger at least partially blocks a material outlet of the longitudinal conveyor. This reduces the throughput of paving material to the paving screed, which is particularly disadvantageous with large layer thicknesses, as these require an increased quantity of paving material.
From EP 0 849 398 A1, a road finisher is known whose rear section can be lifted for paving thick layers. This is achieved by providing a vertical guidance, which can be adjusted in height by means of a hydraulic positioning cylinder, between a crawler undercarriage and a chassis of the road finisher. At the front, the chassis is rotatably mounted on the crawler undercarriage. A disadvantage of this system is the high loads on the hydraulic positioning cylinders, which essentially carry the weight of the lifted chassis completely. Therefore, stability of the road finisher also suffers.
Other road finishers with a chassis that can be lifted at least in a rear region are known from U.S. Pat. No. 4,801,218 A and 3,901,616 A. Also, here high forces act on hydraulic positioning cylinders, which carry the weight of the chassis essentially completely.
From the brochure “CR600 SERIES PAVER & MTV” from BOMAG, a further system for lifting the chassis in relation to the undercarriage in the rear region of a road finisher is known as “Frame Raise System”. In this system, a large circular disc is arranged vertically at the chassis in the paving direction of the road finisher. The disc is rotatably mounted along its circumference on the chassis. The disc can thus be rotated around a main axis of rotation running through its center and transverse to the direction of the road finisher. Eccentrically to the main axis of rotation, a connection to the road finisher's undercarriage is provided on an outer surface of the disc which can be rotated about a side axis transverse to the paving direction. The disc can be rotated in its support on the chassis by means of a hydraulic cylinder. When the disc is rotated, the eccentricity of the connection between the disc and the undercarriage changes the mutual height relationship between the chassis and the undercarriage at the rear of the road finisher. Although the weight of the chassis no longer has to be borne entirely by the hydraulic cylinder, this system still has to apply high forces to rotate the disc when lifting the chassis. Also, when holding the chassis in a certain height position, high loads are applied to the hydraulic cylinder.